In the frame relay networks, the Frame Transfer Priority (hereinafter called FTP) service definition distinguishes between FTP indices and FTP classes. A frame transfer priority index identifies in the setup message the user's request for a frame transfer priority to be assigned to the SVC (Switched Virtual Connection). An FTP index is an integer taking a value from 0 to 15. The higher the FTP index, the higher the priority of the requested FTP service.
An FTP class allows a network to distinguish between frame relay SVCs and PVCs according to the FTP services to which they are assigned during call establishment (in the case of SVC) or provisioning (in the case of PVC). When a frame relay SVC enters the active state, frames of SVCs assigned to a high FTP class are processed and transmitted before SVC frames assigned to lower FTP classes. There are a maximum of 16 different FTP classes.
A salient aspect of the FTP capability definition is the decoupling between FTP indices and classes. The reason for this decoupling is to provide service providers with flexibility to tailor the FTP capability for customers needs. With the distinction between FTP indices and classes, a service provider will be able to support a number of FTP classes of its choice while at the same time accepting 16 different FTP indices. It is therefore clear that when less than 16 FTP classes are supported, several FTP indices will have to be grouped into one or more FTP classes.
The decoupling between FTP indices and classes, however, creates the following disadvantages:
According to the FTP capability definition, it is not possible to infer from the FTP index the frame transfer priority to be assigned to a SVC. Of course this information can be obtained from the service provider of a user. PA1 Different networks may map the same FTP index to different FTP classes. When a SVC has to traverse multiple networks, the exact FTP service assigned to the SVC is not clear. This problem of mapping differences may be resolved to provide a homogenous FTP service but it requires prearranged bilateral agreements between network operators.
The invention addresses to this problem of the decoupling between FTP indices and classes. The invention introduces a parameter called frame transfer normalized priority (hereinafter called FTnP) which is a precise and uniform measure of the FTP service assigned to a frame relay SVC or PVC. It removes the influence caused by the number of FTP classes which can vary from one network to another and by the multiple mappings of FTP indices to classes.